Many of today's search engine services, such as Google, Yahoo and Overture, allow users to search for information that is accessible over the Internet. These search engine services allow users to search for web pages and other Internet-accessible resources that may be of interest to the users. Typically a user submits a search query to the search engine and the search engine returns a set of web pages to the user. The user then clicks on a link and is taken to the selected website.
In the context of electronic commerce (e-commerce), search engines often perform searches for products based on the user's query. For example, once the user has navigated to a particular merchant's website, they may search for a particular product. The search service would then identify the relevant products and display them to the user. It is often useful to rank the products in a particular order in an attempt to display the most relevant product first followed by less relevant products. As no such ranking function is absolutely perfect, it is also desirable to minimize the error of the ranking to the lowest amount possible.